Many air check valves presently being used in bulk haul transport for handling powdered solids, which are unloaded (or loaded) by compressed air, have been adapted for use from equipment originally designed for liquid flow. Accordingly they are generally heavy and expensive, and are usually in the form of a swing type valve many times aided in its movement toward a closed position by gravity. Thus, such prior art devices many times cannot be mounted in all positions in the conduit but instead must be mounted in a predetermined position so that the check valve member can operate properly and in the manner in which it was designed, and as for example in connection with the aforementioned swing type check valve.
Other lighter weight check valve mechanism for bulk product transport have been proposed, wherein a swingable valve plate on an apertured valve body is biased toward closed position by spring means, so that such valve can be positioned in a great plurality of positions in a conduit assembly, without affecting the operation of the valve plate in its opening and closing movements. However, such prior art arrangements usually require rather complex arrangements for positioning and sealing the check valve with respect to the conduit assembly, all of which complicate the assembly and disassembly of the check valve with and from the conduit assembly, resulting in increased initial costs of installation, as well as greater maintenance costs in the event of the need to repair the check valve. Moreover such lighter weight valve mechanisms generally are adapted for use with a predetermined size or diameter of conduit, and are not readily adaptable for use with other conduit diameters.